\tracingonline=2
\tracingcommands=2
\tracingmacros=2
\tracingrestores=2

% control->control
\futurelet\x1\relax
\show\x

\futurelet\y1\relax
\show\y

\futurelet\:1a \show\:

% expandable tokens
\futurelet\x\number20
\show\x

% command
\futurelet\x\count10=20
\show\x
\showthe\count10

\end

